Abstract
References
1.Occupational Diseases mdash; A Guide to Their Recognition . US Department HEW, NIOSH No. 77181 . Revised Edition , June 1977 .
2.
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, (ed): Occupational Medicine, Principles and Practical Applications . Year Book Medical Publishers , Chicago-London , 1975 .
3.An Identification System for Occupationally Hazardous Materials . US Department HEW, NIOSH No. 75 126 , 1974 .